Seismologists dismiss claims of imminent Chile quake

[SANTIAGO] A study of Chile's 2010 earthquake that suggested the country could be hit by another magnitude 8 earthquake in the near future has been branded "alarmist" by Chile's seismology experts.

Published in Nature Geoscience this week (30 January), the study said that last February's quake — which occurred in the Maule region and killed more than 500 people — may have increased the risk of another large event in the affected area.

But Chile's seismology community and the media were stirred by the paper's statement this could happen "in the near future".

The 2010 earthquake occurred in a seismic gap — a section of an active fault that has not slipped in a long time and is therefore most likely to generate future quakes — that has been accumulating stress since a major earthquake in 1835. The authors refer to it as the 'Darwin gap' as Charles Darwin experienced and described the event during his voyage on the Beagle.

It was expected that the 2010 earthquake would have released stress on the gap.

But the paper says that the greatest slips during the event took place in two separate areas to the north of the region — which experienced earthquakes in 1928 and 1960, respectively. The 'Darwin gap' itself experienced little slip, and the amount of stress in the gap has actually increased.

Chilean seismologists Raúl Madariaga, from the geology laboratory of the École Normale Supérieure in France, and Sergio Barrientos, head of the Seismological Service at the University of Chile, both said that this study is the most comprehensive description of the February 2010 earthquake — but challenged its claims of an imminent quake.

Barrientos said there is not enough information to claim another, large magnitude earthquake could happen soon.

"Even though a quake magnitude 7 or more can happen in the area, we lack information about the situation before the earthquake — the pre-stress — to estimate that," he told SciDev.Net.

Considering that accurate seismological data exists only from the 1960s onwards, and that only six major earthquakes have occurred worldwide since then, "drawing statistics [about the behaviour of earthquakes] from such a small sample is not very sound," he said.

"Therefore, I took the paper's announced risk as a [scientific] exercise rather than a prediction."

Madariaga said that the study also failed to consider a poorly known earthquake that hit Concepción, a town on the fault line, in 1960 that may have released some stress.

"I would avoid spreading alarmist announcements that are not possible to found [in data]," he said.